Chemistry questions, help to solve, correct answers will be rewarded

It is a physical change.

Everything else is basic.

5.Gunpowder Papermaking (chemical impurities) Yin Shang era Spring and Autumn period (this does not belong to chemistry, right?) ）

6.Burn dazzling white light hot white magnesium oxide.

7.Cloudy white calcium carbonate. Look

d c c c

Gunpowder, papermaking, Xia and Shang periods, Spring and Autumn periods.

Burning, light, heat, white, magnesium oxide.

Cloudy, white, calcium carbonate.

DCCC gunpowder, papermaking, Xia and Shang periods, Spring and Autumn periods.

Burning, dazzling white light, heat, white powder, magnesium oxide.

Cloudy, white, calcium carbonate.

...The weakness of the liberal arts floats by... The answer to throwing dice is ,,。 Hey.

Tri-state change).

Alcohol flammability).

I learned it in junior high school).

Literate people can answer).

5.gunpowder, papermaking (chemical impurities); Yin Shang era, Spring and Autumn era (test comprehensive ability. ）

6.Burn dazzling white light hot white magnesium oxide. (The most classic junior high school chemistry topic) 7Cloudy white calcium carbonate. (Ibid.).

5.Gunpowder, papermaking, Bronze Age (Xia Shang), Spring and Autumn Period and Warring States Period.

6.Intense burning, white light, heat, white, magnesium oxide.

7.Cloudy, white, calcium carbonate.

Mol metal A reacts with a sufficient amount of dilute sulfuric acid.

Liters of hydrogen are released under the standard condition of Nadan.

A should be presented with what valency should be presented. Let the valency of a be +n, then the cation it forms is an+. a + nh+ an+ +n 2)h2 molar ratio a :

h2 = 1 : n/2) =2 : n ..

1) In the standard case, the molar volume of H2 = l The number of moles used to generate H2 = = The number of moles of a used in mol = mol Molar ratio a : H2 = : = 2 :

3 ..2) Compare annihilation (1) and (2): 2:

N = 2 : 3 The valency of n = 2 = 2 A is burned in a sufficient amount of oxygen.

The solid mass has increased by 4 grams.

aThere is no variation.

Then what is the atomic weight of a 2a + o2 2ao molar ratio a : o2 = 2 : 1 molar mass of o2 = 16x2 = 32 g mol-1 moles of o2 = mass molar mass = 4 32 = mol number of mol a = = molar mass of mol a = mass number of moles = 18 g relative atomic weight of mol-1 a = 18 =

The mass fraction of N element in NH4NO3 was (14 2) (14 2 + 1 4 + 16 3) = 35%.

The nitrogen content in the sample of ammonia nitrate is 30%, assuming a purity of x

then, 35%x=30%.

The solution is x=

Ammonia nitrate NH4NO3 ammonia content = 14*2 (14 + 4 + 14 + 16 * 3) * 100% = 35%.

Then the purity of the sample = 30% 35% * 100% =

reversible reaction).

After adding NH4Cl crystal to the body, the concentration of NH4+ becomes larger, so that the anti-aggressive segment should be reversed, the concentration of OH- becomes smaller, and the pH decreases, so.

Color. Shallow.

Choose C because the ammonia is originally alkaline, so the dropping phenolphthalein is red, NH4Cl is a strong acid and weak alkali salt, its solution is acidic, after adding ammonia Qi Xiju, Lu Chun has a high change and neutralization reaction, and the alkalinity of the solution becomes weaker, so the red becomes lighter.

Grams of sodium produce 4 grams of sodium hydroxide, so the solute mass is a segment of 4 grams of tangerine, and at the same time the resulting hydrogen overflows, a total of grams, so the total mass of the solution is (100+ grams. Therefore, the quality score of regret is the expression of item d.

The phenomenon that most particles can pass through the gold leaf without changing the original direction of travel, proving that there are very few particles that hit the nucleus, so the size of the nucleus is small.

Phenomenon Due to the repulsion of the same sex, the particles change their original direction, or are ** back, but are not adsorbed. Hence it can be proved that the nucleus of an atom has a positively charged nucleus.

Phenomenon There is a part of the particle is ** back, the particle is a helium nucleus, which is composed of two protons and two neutrons, only the mass of the atomic nucleus is large, the particle is ** back. Hence it can be proved that the nucleus mass is large. It can also be used to prove that the nucleus is positively charged.